A 280Z
Fuel Pumps
I think you may have underestimated the size of the pump you need, the one you have installed is rated at 20 gallons per hour.
The one you have removed looks like the Carter 70 gallon per hour pump which although noisy is spec’ed right for an L28 with side drafts and a cam.
The problem is timing when you accelerate hard the floats drop and you need volume to fill the float bowl fast or the engine will go lean, if you grab another gear you will make the problem even worse as the emulsion tube will be only half covered in fuel so again a lean mixture. The small pump with be fine for non-aggressive driving so let your nana drive it till you get a better pump.
To keep my engine from going lean when pushing it hard I am using a 140 gallon per hour pump, I don’t burn all the fuel but to keep the carbs full and get stable mixture in the time available I need the volume of fuel that the larger pump can deliver. This issue was discovered when doing dyno runs, the engine would lean out when held at redline for just a few seconds.
Cheers
Ricky
The one you have removed looks like the Carter 70 gallon per hour pump which although noisy is spec’ed right for an L28 with side drafts and a cam.
The problem is timing when you accelerate hard the floats drop and you need volume to fill the float bowl fast or the engine will go lean, if you grab another gear you will make the problem even worse as the emulsion tube will be only half covered in fuel so again a lean mixture. The small pump with be fine for non-aggressive driving so let your nana drive it till you get a better pump.
To keep my engine from going lean when pushing it hard I am using a 140 gallon per hour pump, I don’t burn all the fuel but to keep the carbs full and get stable mixture in the time available I need the volume of fuel that the larger pump can deliver. This issue was discovered when doing dyno runs, the engine would lean out when held at redline for just a few seconds.
Cheers
Ricky
Hi RickyRicky wrote:I think you may have underestimated the size of the pump you need, the one you have installed is rated at 20 gallons per hour.
The one you have removed looks like the Carter 70 gallon per hour pump which although noisy is spec’ed right for an L28 with side drafts and a cam.
The problem is timing when you accelerate hard the floats drop and you need volume to fill the float bowl fast or the engine will go lean, if you grab another gear you will make the problem even worse as the emulsion tube will be only half covered in fuel so again a lean mixture. The small pump with be fine for non-aggressive driving so let your nana driver it till you get a better pump.
To keep my engine from going lean when pushing it hard I am using a 140 gallon per hour pump, I don’t burn all the fuel but to keep the carbs full and get stable mixture in the time available I need the volume of fuel that the larger pump can deliver. This issue was discovered when doing dyno runs, the engine would lean out when held at redline for just a few seconds.
Cheers
Ricky
You are right mate it can't keep up with the flow. Looking at solutions now.
Cheers mate
Time to solve my fueling issues once and for all (hopefully)
So my experiments with the Fuel Flow pumps was an epic fail, even rocking two of them wouldn't do the trick. Did what I should have done from the start and got another tried and true Carter pump. Ordered the black "competition" version as it is meant to flow the most. To my surprise it is actually not that loud which is a bonus.
Swapped out the dead head style regulator I was using as I wanted to switch to a return line setup as I think I was getting some vapor lock issues also.
Here you can see the return line off the last carb. Also hooked up a fuel pressure gauge so I can see what is happening while driving.
So far things are looking good, getting rock solid pressure throughout the rev range now so fingers crossed problem is solved..
So my experiments with the Fuel Flow pumps was an epic fail, even rocking two of them wouldn't do the trick. Did what I should have done from the start and got another tried and true Carter pump. Ordered the black "competition" version as it is meant to flow the most. To my surprise it is actually not that loud which is a bonus.
Swapped out the dead head style regulator I was using as I wanted to switch to a return line setup as I think I was getting some vapor lock issues also.
Here you can see the return line off the last carb. Also hooked up a fuel pressure gauge so I can see what is happening while driving.
So far things are looking good, getting rock solid pressure throughout the rev range now so fingers crossed problem is solved..
So a problem that some people have with triple Mikunis is a slight lean spot or 'stutter' when you stab on the gas. My car has always had this same issue so wanted to try and get rid of it if possible. It is more noticeable when the car is hot and has been idling in traffic for a while. After doing some reading it sounds like it is caused by fuel in the accelerator pumps boiling and thus not providing enough fuel when you initially hit the gas. Lots of people fit heat shields under the carbs to keep them a bit cooler so I thought Id give it a go too.
Made up an alloy shield which while hopefully helping with keeping heat off the carbs will also have the added bonus of stopping any fuel leaks from dripping onto the hot extractors.
My 44s also came with additional cooling blocks attached to the accelerator pumps (Thanks to Mike for pointing out what these things actually were). Apparently they were used in racing applications back in the day? I figure if I have them might as well use them right.
I took a fuel feed from the in and out of the fuel rail and plumed in the cooling blocks. Yes there is way too much AN fitting action going on, I think I might make a proper fuel rail up to get rid of some of it...
Here you can see the fuel line under each carb linking the circuit together.
Everything back together with heat shield added.
Happy to say it looks to have completely resolved the lean spot on initial throttle stab. If anything now the wide-band is showing things are a bit rich but that's something I can possibly tune out with some jet changes. Car no longer stumbles when you first hit the gas so I am claiming a win...
Made up an alloy shield which while hopefully helping with keeping heat off the carbs will also have the added bonus of stopping any fuel leaks from dripping onto the hot extractors.
My 44s also came with additional cooling blocks attached to the accelerator pumps (Thanks to Mike for pointing out what these things actually were). Apparently they were used in racing applications back in the day? I figure if I have them might as well use them right.
I took a fuel feed from the in and out of the fuel rail and plumed in the cooling blocks. Yes there is way too much AN fitting action going on, I think I might make a proper fuel rail up to get rid of some of it...
Here you can see the fuel line under each carb linking the circuit together.
Everything back together with heat shield added.
Happy to say it looks to have completely resolved the lean spot on initial throttle stab. If anything now the wide-band is showing things are a bit rich but that's something I can possibly tune out with some jet changes. Car no longer stumbles when you first hit the gas so I am claiming a win...
Interesting. We have the same issue with our Mikunis - was looking into a heatshield myself. How much work was involved and did it require the removal of the carbs from the manifold to fit?
Not a huge job really. No you would not have to take of the carbs to fit, I did to make life a little easier for measuring and making brackets etc. I didnt really want to fit one as I prefer the cleaner look but seems to have helped with my problem so was worth doing.Pedey wrote:Interesting. We have the same issue with our Mikunis - was looking into a heatshield myself. How much work was involved and did it require the removal of the carbs from the manifold to fit?
So the cooling bodies work go figure that is why mikuni built them. These blocks are not common and only found on the last of the 44phh S5 carbs
Last edited by nzeder on Fri Apr 24, 2015 6:50 am, edited 3 times in total.
So have not driven the car at all over winter due to doing stupid stuff like building a new house and moving etc. But one bonus is built a decent shed to fill with cars...
Have lots of small things to do to the car over summer. New jets for the triples to test, LSD to go in etc. One small thing I have done is convert my speedo.
Being as my car is originally from the the USA it had a MPH speedo which was a bit of a pain in the ass. I found a guy in Sweden who had designed his own re-pro KMPH face plates and had done a small production run so bought one to give a try.
The quality is not to bad so I stripped down my old speedo and swapped over the faces. I now have a KMPH version so all good.
I also swapped out the old clock in the dash as it has never worked. I found an oil temp gauge with a similar look to the stock gauges.
LSD install next on the list.
Have lots of small things to do to the car over summer. New jets for the triples to test, LSD to go in etc. One small thing I have done is convert my speedo.
Being as my car is originally from the the USA it had a MPH speedo which was a bit of a pain in the ass. I found a guy in Sweden who had designed his own re-pro KMPH face plates and had done a small production run so bought one to give a try.
The quality is not to bad so I stripped down my old speedo and swapped over the faces. I now have a KMPH version so all good.
I also swapped out the old clock in the dash as it has never worked. I found an oil temp gauge with a similar look to the stock gauges.
LSD install next on the list.
Awesome, who built the shed? It looks really good, my old man has a big barn shed similar style good for the car collection. The gauge changes look the part too, who needs to tell the time when you're speeding down the highway anyway
In a long distance relationship with my 260z
all hail the mighty SHED!! can never have to much space for cars
still drawing mine up!
Is it to have a hoist? amongst other mancave things......
still drawing mine up!
Is it to have a hoist? amongst other mancave things......
1973 240Z - NZ new - RB25det build in progress
1973 240Z - USA new - 1 owner! In the drivers seat right now. Home soon.
1973 240Z - USA new - 1 owner! In the drivers seat right now. Home soon.
So I managed to score a z31 CLSD R200 with a NISMO center by a lucky fluke earlier this year. As far as I am aware it has a 3.7 ratio.
Ripped out the old 3.3 (I was told, will open and confirm) open wheeler. Only thing that needs swapping over is the front drive shaft flange as the Z31 one is different. Cool thing about this swap is the S30 stub axles plug straight into the Z31 CLSD center so it is a really easy conversion.
And the uni half shafts as they were looking pretty blue and shit. I actually have a set of Z31 CV half shafts I want to install to get rid of the uni's but I still have to suss out some adapters for that job so uni's stay for now.
I dont know what state the new CLSD is in but looked pretty tidy inside from what I can tell so best just to throw it in and see what happens
Gave the diff and half shafts a tidy up
Threw it all back in with some new oil and job done. Went out for test drive and nothing blew up, it is not overly noisy at all and seems to lock up OK. I tried to do a mandatory sweet skid but only succeeded in skidding up my shit house clutch so that is now on the list to get replaced stat.
Ripped out the old 3.3 (I was told, will open and confirm) open wheeler. Only thing that needs swapping over is the front drive shaft flange as the Z31 one is different. Cool thing about this swap is the S30 stub axles plug straight into the Z31 CLSD center so it is a really easy conversion.
And the uni half shafts as they were looking pretty blue and shit. I actually have a set of Z31 CV half shafts I want to install to get rid of the uni's but I still have to suss out some adapters for that job so uni's stay for now.
I dont know what state the new CLSD is in but looked pretty tidy inside from what I can tell so best just to throw it in and see what happens
Gave the diff and half shafts a tidy up
Threw it all back in with some new oil and job done. Went out for test drive and nothing blew up, it is not overly noisy at all and seems to lock up OK. I tried to do a mandatory sweet skid but only succeeded in skidding up my shit house clutch so that is now on the list to get replaced stat.